The Portillo moment was the declaration of the result for the Enfield Southgate constituency in the 1997 general election, at 3:01 a.m. on 2 May 1997. The Labour Party candidate, Stephen Twigg, defeated the sitting MP, Conservative cabinet minister Michael Portillo. The result was perceived as a pivotal indication that the Conservatives would be voted out of office after 18 years and that Labour would win the election by a substantial majority.

The late-night declaration of the result became the subject of the question "Were you still up for Portillo?", asking whether a person had remained awake until after 3 am to see or hear the key general-election results. "Portillo moment" has become a metaphor for an indication of a sudden and significant change in political fortunes, particularly the unseating of a leading MP (especially a cabinet minister) at a general election.

Michael Portillo was first elected to the House of Commons to represent Enfield Southgate at a by-election in 1984. The constituency included largely suburban areas in the west of the London Borough of Enfield. Portillo retained the seat at the 1987 general election and won with a comfortable majority of 15,563 in the 1992 general election.

By 1997, Portillo was Secretary of State for Defence in the Conservative government. He had developed a reputation as one of the leading lights of the right wing of the Conservative Party and was considered a possible candidate to follow John Major as party leader following the 1997 general election. The Labour Party candidate, Stephen Twigg – 30 years old, openly gay and relatively unknown – was considered unlikely to be able to unseat Portillo even in the Labour-leaning national environment. They had previously met when Portillo addressed Twigg's school during the latter's schooldays.

The Conservatives held a small majority in the House of Commons following the 1992 general election and remained in power for almost the maximum possible five years as their majority was gradually reduced at successive by-elections. Coming into the 1997 general election, Labour had held a substantial lead in the national polls for a considerable time, but Portillo's seat was still considered safe. However, a poll in The Observer newspaper the Sunday before the election showed that Portillo held a lead of only three percentage points.

After the polls had closed but before the result was formally announced, Portillo was interviewed live by Jeremy Paxman on BBC Television. By that stage, exit poll results had been revealed and predicted a Labour landslide nationally, and Portillo was privately aware of his possible defeat, although this was unknown to the public, who right up to the result were still expecting Portillo to be the next Tory leader. Portillo dismissed the national exit poll but struggled to answer Paxman's question, "Are we seeing the end of the Conservative Party as a credible force in British politics?"

At the local election headquarters, Portillo said, "Everyone around me, including the Labour workers, behaved towards me as though I'd been bereaved. They looked apologetic. I know I was a national figure of hate for Labour but you can only hate at a distance. The people in that room were Labour councillors that I'd worked with and liked. All evening, they treated me with courtesy and consideration."

Twigg and the other candidates also knew the results shortly before the formal announcement. Twigg was shocked but determined to keep a neutral expression during the announcement to maintain viewers' excitement to the last moment.